This invention relates in general to seals and more particularly to seals that are highly compact, yet are extremely effective in retaining lubricants in and excluding contaminants from a sealed cavity.
The steering knuckles of front wheel drive automobiles carry the bearings on which the front wheels rotate, each bearing in effect being received in its steering knuckle and in turn receiving a rotatable hub to which a wheel is bolted. Little space exists in this mechanism for accommodating the bearing, and as a result the bearings for front wheel drive automobiles are highly compact. Of course such bearings require seals to retain lubricants and to exclude contaminants, and to achieve an effective spread, that is sufficient spacing between the two rows of rolling elements in the bearing, the seals must occupy as little space as possible. Typically the seals are fitted into the ends of the bearing where they also serve to unitize the bearing for handling purposes.
Sometimes a secondary seal is installed between the knuckle and the hub to provide an extra measure of protection, particularly beyond the main seal at the inboard end of the bearing, but if the secondary seal does not establish an effective barrier, it can be a detriment that diminishes the life of the bearing. For example, if the secondary seal is of poor quality, or is damaged, or is around a poor quality mating surface, it will allow contaminants such as water to work into the space between it and the main seal and indeed will trap contaminants in that space. These contaminants eventually destroy the main seal and the bearing which the main seal is designed to protect. Thus, an ineffective secondary seal is worse than no secondary seal at all.
Aside from the potentially destructive effects that a secondary seal may have, a secondary seal constitutes still another part in an already complicated assembly and requires machined surfaces where it is mounted and at the mating surface against which it bears. This, of course, adds to the cost of the front wheel drive assembly.
A typical front wheel bearing for front wheel drive automobiles is supplied as a unit and includes a unitary outer race, which at its ends receives and holds the seals for the bearing. These seals bear against the inner race. The seals of the present invention when installed at the ends of a bearing for a front wheel drive automobile establishes extremely effective barriers-ones that need not be supplemented by secondary seals. Moreover, they create only minimal drag and thus require little torque. The seals not only prevent the lubricant that is within the bearing from escaping, but actually pump the lubricant back into the interior of the bearing.